1. Field of the Invention
The present invention relates in general to the field of medical-electronics. More particularly, the present invention relates to heart stimulating devices commonly known as heart pacers.
2. Description of Prior Art
Heart stimulating devices have been known for some time. Several years ago, heart stimulating devices which provide stimulation at a fixed or constant rate were developed. They were deficient since they created competitive problems with the natural or spontaneous heartbeat. More recently, heart stimulating devices which supply stimulation to the heart only when required have been developed, and these pacers solved the competition problem. And even more recently, heart pacers that supply stimulation only when required and in proper sequence to two chambers of the heart, the atrium and ventricle, have been developed.
In all pacers designed for use within the body of a patient whose heart is to be stimulated, a portable power supply is necessary. Ordinarily, a battery power supply is used, where it is desirable for battery life to be of long duration. For example, pacer batteries of chemical composition can be operative for as long as 2 years or more. More recently, nuclear batteries and other sources of circuitry energization have been developed. However, these newer methods of circuitry energization are attendant with certain severe technical problems which do not burden pacers powered or energized by conventional chemical batteries. But, chemical batteries have leakage problems to be described below.
A mercuric-oxide-zinc chemical composition is a typical chemical composition for a pacer battery. This battery is the type that requires venting of fluids as internal chemicals mutually react. The liquid which is vented or discharged from the battery is usually an aqueous solution of sodium hydroxide or potassium hydroxide. This aqueous solution of either of these electrolytes can provide an effective leakage conductive path for current flow between positive and negative electrodes of a battery cell. Alternatively, or additionally, water from regions external to the implanted pacer may seep into the pacer through various apertures, (for example, the aperture where the catheter inter-connects with the pacer circuitry), and may likewise electrically connect positive and negative electrodes of a battery cell causing a leakage path for that particular cell. Leakage current flow can substantially reduce effective life of a battery, and thus substantially reduce the pacer's life.
Approximately 70% of pacers that are presently being used fail due to battery exhaustion. Battery exhaustion, as earlier noted, is increased by leakage paths between positive and negative electrodes of individual battery cells. There is evidence which indicates that with regard to mercury battery cells, approximately half of the potential energy is utilized for productive work; therefore, it is possible that the other half of potential energy of the mercury cell is wasted in leakage currents across grommets of prior art design. The present invention is an improvement to conventional chemical batteries subject to this leakage problem. The present invention can extend battery life possibly up to 100%.